The use of microwave heating in industrial processing of food has been undergoing development for the last 15 years. The two processes of main interest are pasteurization and sterilization. In each case the objectives have been to develop continuous processes that can reduce energy consumption and improve the product quality, while maintaining microbiological integrity. Microwave sterilization is a comparatively long term objective due to the difficult engineering required to handle the higher temperatures and pressures, and the fact that the sterilization process is subject to very stringent regulatory requirements and process acceptance. As a result, it is the comparatively simpler pasteurization process that is mainly of immediate interest to the food industry. Microwave pasteurization of breads and pastas has been in use in Europe for several years and there is a desire to extend the process to other food products.
The objective is to attain a pasteurization temperature, e.g. 70.degree.-90.degree. C., as quickly as possible and to reduce the time of holding at this temperature, while maintaining quality, i.e. avoiding degradation and ensuring microbiological safety. Non-uniform heating has been the major obstacle to be overcome in the achievement of microwave pasteurization.